Cast dumbbell



FIG. 1 is a perspective view of a cast dumbbell, showing my new design;

FIG. 2 is a view in front elevation;

FIG. 3 is a view in end elevation, the two ends being mirror images of one another;

FIG. 4 is a top plan view; and,

FIG. 5 is a bottom plan view. 

The ornamental design for a cast dumbbell, as shown and described. 